Milk whey protein is prepared by removing fat and casein from milk, and comprises .alpha.-lactalbumin, .beta.-lactoglobulin and whey albumin. The main whey protein is .beta.-lactoglobulin (.beta.-lg), which constitutes about 50% of the total whey proteins. Large amounts of whey proteins are produced during the manufacturing of dairy products. The nutritional value of whey proteins makes them useful as food ingredients.
Whey proteins can be used as a protein source in desserts; however, it has been difficult to produce whey protein desserts with an acceptable texture without adding carbohydrate gelling agents (Mleko, Milchwissenshaft 52:262-265, 1997). The viscosity of whey protein dispersions is related to the size and shape of the protein molecules. Food proteins, especially whey proteins, are small (&lt;60 kDa) and more spherical in shape compared to carbohydrate hydrocolloids which are large (generally&gt;200 kDa) and rod-like. For coiled molecules, the viscosity is a function of the diameter of the coil and of the extent to which solvent can drain freely through the coil without becoming entrapped by hydrodynamic forces. For a homologous series of rods of constant diameter, the viscosity increases with molecular weight, which is proportional to the length (Cantor and Schimmel 1980, Biophysical Chemistry. Part II: Techniques for the study of biological structure and function, W. H. Freeman and Company, San Francisco, Calif.).
The functionality of a protein or polysaccharide is associated with specific chemical and physical properties of individual macromolecules, interactions with other ingredients, and the processing operations used in producing a given food. Food proteins and carbohydrate hydrocolloids differ in functionality. For example, the viscosity of carbohydrate hydrocolloids can be several hundred times higher than food proteins at the same concentration. To be acceptable for use in food products, whey protein products must have acceptable physical properties and acceptable mouth feel.
Accordingly, it is desirable to obtain whey protein dispersions with viscosities comparable to that of carbohydrate hydrocolloids.